This invention relates generally to gas turbine engine exhaust nozzles and more particularly, to methods and apparatus for retaining basesheet assemblies within gas turbine engine exhaust nozzles.
At least some known gas turbine engines include an exhaust nozzle including a variable geometry system. The variable geometry system adjusts an area of the exhaust nozzle through the use of flaps and seals. The flaps define discrete sectors of the flowpath, and the seals form the remaining flowpath between adjacent flaps. Because the exhaust nozzles are subjected to high temperatures and thermal gradients as a result of hot combustion gases exiting the engine, the variable geometry systems must maintain a coherent flowpath while shielding the structural components of the variable geometry system.
At least some known flap and seal systems consist of a backbone and a basesheet. The backbone secures the basesheet within the variable geometry system. To facilitate extending a useful life at high temperature operation, at least some known basesheets are fabricated from non-metallic materials, such as ceramic matrix composite (CMC) materials.
At least some known basesheets are attached to the backbone using mechanical fasteners, such as rivets or bolts. Over time, continued thermal expansion may create local stress concentrations within the bolted and riveted joints. Furthermore, continued thermal cycling may loosen such mechanical fasteners. Other known basesheets are attached to the backbone with embedded attachments. Such attachments rely primarily on an interlaminar tensile strength of the basesheet material to remain in place. Because such tensile strength may be a weakest load path through the basesheet, continued thermal cycling may loosen such embedded attachments and induce potentially damaging stresses into the basesheet.
In one aspect, a method for assembling a flap and seal system for a gas turbine engine exhaust nozzle including a plurality of backbone assemblies is provided. The method comprises attaching an attachment system including at least one strap to a basesheet, and coupling the basesheet to a backbone using the attachment system strap.
In another aspect, an assembly for a gas turbine engine exhaust nozzle is provided. The assembly comprises a basesheet, a backbone, and an attachment sub-assembly. The attachment sub-assembly including at least one strap attached to the basesheet and configured to couple the basesheet to the backbone.
In a further aspect, a gas turbine engine is provided. The gas turbine engine comprises a variable engine exhaust nozzle including a flap and seal system coupled to the engine exhaust nozzle. The flap and seal system includes a basesheet, a backbone, and an attachment assembly. The attachment assembly is configured to couple the basesheet to the backbone, includes at least one strap attached to the basesheet for coupling the basesheet to the backbone.